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Groups > linux.kernel > #1664405

[PATCH v4 04/16] perf util: add const modifier to buf in "writen" function

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Make buf in helper function "writen" constant to simplify
the life of its callers.

This requires to hack a cast of buf prior to passing it to "ion"
which is simpler than the alternative of reworking the "ion"
function to provide a read and a write paths, the latter with
constant buf argument.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
 tools/perf/util/util.c | 6 ++++--
 tools/perf/util/util.h | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 28c9f335006c..0d8d7b8b2949 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -259,6 +259,7 @@ static ssize_t ion(bool is_read, int fd, void *buf, size_t n)
 	size_t left = n;
 
 	while (left) {
+		/* buf must be treated as const if !is_read. */
 		ssize_t ret = is_read ? read(fd, buf, left) :
 					write(fd, buf, left);
 
@@ -286,9 +287,10 @@ ssize_t readn(int fd, void *buf, size_t n)
 /*
  * Write exactly 'n' bytes or return an error.
  */
-ssize_t writen(int fd, void *buf, size_t n)
+ssize_t writen(int fd, const void *buf, size_t n)
 {
-	return ion(false, fd, buf, n);
+	/* ion does not modify buf. */
+	return ion(false, fd, (void *)buf, n);
 }
 
 size_t hex_width(u64 v)
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 5dfb9bb6482d..fc6555e48422 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -49,7 +49,7 @@ int copyfile_mode(const char *from, const char *to, mode_t mode);
 int copyfile_offset(int fromfd, loff_t from_ofs, int tofd, loff_t to_ofs, u64 size);
 
 ssize_t readn(int fd, void *buf, size_t n);
-ssize_t writen(int fd, void *buf, size_t n);
+ssize_t writen(int fd, const void *buf, size_t n);
 
 size_t hex_width(u64 v);
 int hex2u64(const char *ptr, u64 *val);
-- 
2.13.1.508.gb3defc5cc-goog

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[PATCH v4 00/16] perf tool: add meta-data header support for pipe-mode David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 16/16] perf header: add event desc to pipe-mode header David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 03/16] perf header: fail on write_padded error David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 13/16] perf header: change FEAT_OP* macros David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 02/16] perf header: add PROCESS_STR_FUN macro David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 10/16] perf header: use struct feat_fd in read header records David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 07/16] perf header: use struct feat_fd for print David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 01/16] perf header: encapsulate read and swap David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 04/16] perf util: add const modifier to buf in "writen" function David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 11/16] perf header: make write_pmu_mappings pipe-mode friendly David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 09/16] perf header: don't pass struct perf_file_section to process_##_feat David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
    Re: [PATCH v4 09/16] perf header: don't pass struct  perf_file_section to process_##_feat Jiri Olsa <jolsa@redhat.com> - 2017-06-13 21:00 +0200
      Re: [PATCH v4 09/16] perf header: don't pass struct perf_file_section  to process_##_feat David Carrillo-Cisneros <davidcc@google.com> - 2017-06-14 04:00 +0200
  [PATCH v4 12/16] perf header: add a buffer to struct feat_fd David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
    Re: [PATCH v4 12/16] perf header: add a buffer to struct feat_fd Jiri Olsa <jolsa@redhat.com> - 2017-06-13 21:00 +0200
      Re: [PATCH v4 12/16] perf header: add a buffer to struct feat_fd David Carrillo-Cisneros <davidcc@google.com> - 2017-06-14 04:00 +0200
  [PATCH v4 14/16] perf tool: add show_feature_header to perf_tool David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
    Re: [PATCH v4 14/16] perf tool: add show_feature_header to perf_tool Jiri Olsa <jolsa@redhat.com> - 2017-06-13 21:00 +0200
  [PATCH v4 06/16] perf header: add struct feat_fd for write David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  [PATCH v4 08/16] perf header: use struct feat_fd to process header records David Carrillo-Cisneros <davidcc@google.com> - 2017-06-13 06:40 +0200
  Re: [PATCH v4 00/16] perf tool: add meta-data header support for  pipe-mode Jiri Olsa <jolsa@redhat.com> - 2017-06-13 21:00 +0200
    Re: [PATCH v4 00/16] perf tool: add meta-data header support for pipe-mode David Carrillo-Cisneros <davidcc@google.com> - 2017-06-14 08:50 +0200
  Re: [PATCH v4 00/16] perf tool: add meta-data header support for  pipe-mode Jiri Olsa <jolsa@redhat.com> - 2017-06-13 21:00 +0200
    Re: [PATCH v4 00/16] perf tool: add meta-data header support for pipe-mode David Carrillo-Cisneros <davidcc@google.com> - 2017-06-14 09:00 +0200
      Re: [PATCH v4 00/16] perf tool: add meta-data header support for  pipe-mode Jiri Olsa <jolsa@redhat.com> - 2017-06-14 09:30 +0200
        Re: [PATCH v4 00/16] perf tool: add meta-data header support for pipe-mode David Carrillo-Cisneros <davidcc@google.com> - 2017-06-14 20:40 +0200

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